This invention relates to crack detection in turbomachinery components and in particular to inspection of gas turbine buckets for cracks using an eddy-current sensor without disassembly of the gas turbine.
Inspection of turbomachinery components such as rotating gas turbine blades for cracks which may have developed during service operation has previously been performed either by partial disassembly of the machine and use of fluorescent penetrant tests, i.e., by examining under ultraviolet light parts which have been treated with fluorescent dye penetrants, or by inserting an optical borescope through the casing of the machine and viewing the resulting transmitted images of the inspected part on a screen located outside the machine. The dye penetrant method, though accurate, requires costly and timeconsuming disassembly of major portions of the gas turbine to gain access to the parts to be inspected and thus is economically unattractive for use in the field or on a frequent basis. The borescope approach, though relatively convenient for field application, is limited in that the optical nature of borescopes make them incapable of detecting minute or sub-surface cracks, which are not visible even under several powers of magnification but whose detection may be vital to prevention of severe damage to the machine.
Accordingly it is a general object of the invention to provide an improved apparatus for inspecting turbomachinery components for cracks and more particularly to provide a crack detection probe which will permit inspection of gas turbine parts without disassembly of the gas turbine.
A further object of the invention is to provide a simple, compact, remotely operable crack detection probe capable of accurately detecting minute cracks in gas turbine buckets without disassembly of the turbine casings.